Field of the Invention
The present invention relates to wireless communication and, more particularly, to a method and apparatus for searching for a control channel in a multi-node system.
Related Art
Recently, an amount of data transfer of a wireless communication network has rapidly increased. The increase in the amount of data transfer attributes to machine-to-machine (M2M) communication and the advent and prevalence of various devices such as smartphones, tablet PCs, and the like, requiring a large amount of data transfer. In order to meet the required a large amount of data transfer, recently, carrier aggregation aimed at effective use of more frequency bands, cognitive radio technology, and multi-antenna technology and multi-base station cooperation technology aimed at increasing data capacity within a limited frequency, and the like have emerged.
A wireless communication network has evolved toward increasing density of accessible nodes around users. Here, nodes may refer to antennas or antenna groups spaced apart from a distributed antenna system by a predetermined interval or greater, or without being limited thereto, nodes may be used in a broader context. Namely, nodes may be a pico-cell base station (PeNB), a home base station (HeNB), a remote radio head (RRH), a remote radio unit (RRU), a repeater, and the like. A wireless communication system having high density of nodes may exhibit higher system performance through node cooperation. Namely, compared to a case in which nodes separately operate as base station (BS), an advanced BS (ABS), a node-B (NB), an eNode-B (eNB), an access point (AP), or the like, without cooperation, if nodes operate like antennas or antenna groups with respect to a single cell under administration of a single control station in their transmission and reception, far better system performance may be attained. Hereinafter, a wireless communication system including a plurality of nodes will be referred to as a multi-node system.
Nodes generally refer to an antenna group spaced apart by more than a predetermined interval from a distributed antenna system (DAS). But nodes may also be defined as a certain antenna group regardless of a distance to the DAS. For example, a base station including cross polarized antennas may be considered as a base station composed of a node configured as an H-pol antenna and a node configured as a V-pol antenna, and the present invention may be applied thereto
Meanwhile, in a multi-node system, a new control channel may be used due to an inter-cell interference and shortage of capacity in existing control channels. Existing control channels may be decoded based on a cell-specific reference signal (CRS), while the new control channel may be decoded based on a user-specific reference signal.
Also, a new control channel may be allocated to a data region, among a control region and a data region of existing subframes. In this case, a new control channel may be allocated to a radio resource region to which two different resource allocation schemes such as non-interleaving and interleaving are applied.
In the multi-node system employing a new control channel, how a terminal (or a user equipment (UE)) searches for the new control channel may be an issue. Namely, how a radio resource region, namely, a search space, to be monitored to search for the new control channel is to be configured and which downlink control information (DCI) format is to be specifically searched in a configured search space may be an issue.